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Abstract:

The present invention relates to an apparatus and a method for the
creation of an impingement jet (P) generating annular swirls (7). The
apparatus includes at least one fluidic switching element (1, 1') having
an inlet branch (2) with an inlet opening (21) via which cooling gas (G)
can be supplied to the fluidic switching element (1), at least two outlet
branches (31, 32) provided downstream of the inlet branch (2) and ending
each in an outlet opening (8), a branching point (4) at which the inlet
branch (2) splits into the at least two outlet branches (31, 32), and
control means (31, 32, S) for controlling the cooling gas (G) flowing in
the inlet branch (2) such that the cooling gas (G) is routed
alternatingly into the one or the other of the outlet branches (31, 32),
with an impingement jet (P) pulsating at a frequency (f) being generated
in each outlet branch (31, 32). Here, the fluidic switching element (1)
is designed and provided for emitting cooling gas at the outlet openings
(8) with a mean outflow velocity (u) and a frequency (f) such that the
impingement jet (P) exiting the outlet openings (8) forms annular swirls
(7). The invention furthermore relates to a turbomachine with an
apparatus of this type.

Claims:

1. Apparatus for the creation of an impingement jet generating annular
swirls, characterized by at least one fluidic switching element having an
inlet branch with an inlet opening via which cooling gas can be supplied
to the fluidic switching element, at least two outlet branches provided
downstream of the inlet branch and ending each in an outlet opening, a
branching point at which the inlet branch splits into the at least two
outlet branches, and control means for controlling the cooling gas
flowing in the inlet branch such that the cooling gas is routed
alternatingly into the one or the other of the outlet branches, with an
impingement jet pulsating at a frequency being generated in each outlet
branch, with the fluidic switching element being designed and provided
for emitting cooling gas at the outlet openings with a mean outflow
velocity and a frequency such that the impingement jet exiting the outlet
openings forms annular swirls.

2. Apparatus in accordance with claim 1, characterized in that the
control means include a periodically fluctuating controlling mass flow
supplied via at least one control supply line to the fluidic switching
element.

3. Apparatus in accordance with claim 2, characterized in that the
control means provide a two-sided control where the controlling mass flow
is supplied via two control supply lines to the fluidic switching
element.

4. Apparatus in accordance with claim 2, characterized in that the
control means provide a one-sided control where the controlling mass flow
is supplied via one control supply line to the fluidic switching element.

5. Apparatus in accordance with claim 1, characterized in that the ratio
between the frequency of the pulsating impingement jet, the mean outflow
velocity of the cooling gas from the outlet openings and the diameter of
the outlet openings is such that the Strouhal number formed with these
values according to the formula Sr=f*d/u is in the range between 0.2 and
2.0, in particular in the range between 0.8 and 1.2.

6. Apparatus in accordance with claim 1, characterized in that the
fluidic switching element is designed in a partition wall arranged at a
distance from an impingement wall to be cooled, where the annular swirls
formed by the impingement jet impact the impingement wall.

7. Apparatus in accordance claim 1, characterized in that the outlet
branches of the fluidic switching element are designed curved.

8. Apparatus in accordance with claim 1, characterized in that the outlet
branches of the fluidic switching element are designed straight.

9. Apparatus in accordance with claim 1, characterized in that the
branching point forms two feedback lobes inside which part of the cooling
gas is routed back in the direction of the inlet branch instead of
flowing into one of the outlet branches.

10. Apparatus in accordance with claim 1, characterized in that the
apparatus has a plurality of fluidic switching elements arranged in the
form of a one- or two-dimensional array.

11. Apparatus in accordance with claim 1, characterized in that two
fluidic switching elements are arranged adjacent to one another and that
two outlet branches of these adjacently arranged fluidic switching
elements are aligned with one another such that annular swirls with
double frequency are present at a defined distance from the fluidic
switching elements.

12. Turbomachine with an apparatus in accordance with claim 1,
characterized in that the fluidic switching element is arranged in the
turbomachine such that the annular swirls formed by the impingement jet
exiting the outlet openings of the fluidic switching element impact a
wall or surface of the turbomachine to be cooled.

13. Turbomachine in accordance with claim 12, characterized in that the
turbomachine is a turbine and the wall or surface to be cooled is that of
a casing, a casing liner or a turbine blade of the turbine.

14. Turbomachine in accordance with claim 13, characterized in that the
surface to be cooled is the rear face of an insert ring arranged in the
area of the rotor of a turbine on the circumference of the turbine
casing.

15. Method for the creation of an impingement jet generating annular
swirls, characterized in that cooling gas is supplied in one fluidic
switching element alternatingly to at least two outlet branches of the
fluidic switching element, where in each outlet branch an impingement jet
pulsating at a frequency is generated and forms annular swirls after
leaving the fluidic switching element.

Description:

[0001] This invention relates to an apparatus and a method for the
creation of an impingement jet generating annular swirls as well as a
turbomachine with an apparatus of this type.

[0002] It is generally known to provide impingement cooling for the
cooling of the components of a turbomachine. Appropriate impingement
cooling configurations subject a component or surface to be cooled to
cooling air, where said cooling air or another fluid from a nozzle
impinges on a surface to be cooled. Impingement cooling configurations
used in turbomachines are operated with stationary impingement jets
providing a stationary supply of cooling air.

[0003] It is known from DE 10 2007 008 319 A1 to provide impingement
cooling while achieving a pulsating supply of cooling air. It was proven
in Janetzke: "Experimentelle Untersuchungen zur Effizienzsteigerung von
Prallkuhlkonfigurationen durch dynamische Ringwirbel hoher Amplitude",
thesis TU-Berlin, 2010, Mensch und Buch Verlag (publishers), that
considerable increases in cooling effectivity can be obtained by a
pulsating supply of cooling air, with a corresponding savings potential
for cooling air mass flow. This is linked to the fact that a pulsating
cooling air supply generates annular swirls, depending on the pulsation
frequency and the pulsation amplitude, said swirls containing cooling
fluid in their core and transporting it from the nozzle outlet to the
impingement plate to be cooled. There the periodic occurrence of annular
swirls leads to a periodic renewal of the fluid and temperature boundary
layer. Depending on the swirl frequency and amplitude or on the swirl
intensity resulting from these values, this can lead to reductions or
increases of the convective heat transfer.

[0004] To create annular swirl structures that considerably increase the
effectivity of impingement cooling, a certain ratio between the frequency
f of the pulsating cooling air supply, the mean nozzle outflow velocity u
and the diameter of the outlet opening emitting the impingement jet has
proven to be advantageous.

[0005] These three parameters are linked as follows using the Strouhal
number Sr, a dimensionless frequency:

Sr=f*d/u.

[0006] It has become clear that a Strouhal number of Sr=0.26 forms the
lower limit for an increase in the heat transfer. Ideally, Strouhal
numbers are in the range between Sr=0.8 and 1.2, so that annular swirl
structures with high cooling efficiency can be created.

[0007] The result is thus that a pulsating cooling air supply with
generation of annular swirls makes possible a considerably improved
impingement cooling efficiency. This however raises the problem of how in
the case of turbomachines, for example thermally highly loaded turbine
components of a jet engine, pulsation of the cooling air can be assured
at the high amplitudes and high frequencies necessary to achieve
effective Strouhal numbers.

[0008] To date, pulsating impingement cooling configurations have only
been tested in the laboratory. In laboratory tests, the pulsation is
usually generated by active actuators, for example valves or siren-like
components. Furthermore, additional resonators are sometimes used for
generating the necessary high amplitudes. Although the active pulse
generators used in laboratory tests attain the necessary high amplitude
and frequency, they are ill-suited for use in a turbomachine due to their
size, their additional weight and their complexity.

[0009] A particular problem from the technical viewpoint is the
combination of the required high frequency resulting from the high
outflow velocities of the impingement jet nozzles used in the
turbomachine to achieve the aforementioned Strouhal numbers, and the
absolutely necessary high amplitude.

[0010] It has furthermore been shown that passive methods for pulsation
generation using Karman swirl nozzles, for example, are not suitable for
generating sufficiently high amplitudes in the targeted Strouhal number
range and hence for increasing the convective heat transfer, cf. here
Herwig at al., 2004, "Warmeubergang bei instationaren Prallstrahlen",
Chemie Ingenieur Technik, 76(2), 84-88.

[0011] The object underlying the present invention is therefore to provide
an apparatus permitting the provision of pulsating impingement jets in
the Strouhal number range between Sr=0.2 and 2 and with high amplitude,
where said apparatus should be suitable to be used for impingement
cooling in turbomachines.

[0012] The present invention provides an apparatus with the features of
Claim 1, a turbomachine with the features of Claim 12 as well as a method
with the features of Claim 15. Embodiments of the present invention
become apparent from the sub-claims.

[0013] In accordance with a first aspect of the invention, at least one
fluidic switching element is therefore provided to create an impingement
jet generating annular swirls, said element having an inlet branch and,
downstream of the latter, at least two outlet branches. Control means are
provided which control the cooling gas flowing in the inlet branch at a
branching point such that the cooling gas is routed into only one of the
outlet branches. The cooling gas is here alternatingly routed into the
one or the other of the outlet branches. In each outlet branch, a
pulsating impingement jet with a frequency f is generated in this way.
This fluidic switching element is designed such that cooling gas can be
emitted at the outlet openings of the outlet branches with a mean outflow
velocity and with a frequency such that the impingement jet exiting the
outlet openings forms annular swirls.

[0014] The solution in accordance with the invention permits, by the use
of a fluidic switching element, generation of annular swirls with a high
amplitude at a defined Strouhal number in the range between 0.2 and 2.0,
and in a frequency range characteristic for turbomachines, without the
incoming main mass flow of the cooling gas needing to be periodically
interrupted to do so.

[0015] In so doing, the alternating routing of the cooling gas into the
two outlet branches of the fluidic switching element provides in the
ideal case an amplitude of 100% of the mean outflow velocity,
corresponding to an on/off jet. The impingement jets provided at the
outlet of the fluidic switching element are thus periodically
interrupted. This is achieved in accordance with the invention without an
active and expensive interruption mechanism.

[0016] In an embodiment of the invention, the control means include a
periodically fluctuating controlling mass flow supplied by means of at
least one control supply line to the fluidic switching element in the
area of the branching point. The controlling mass flow is here smaller
than the mass flow of the cooling gas. The control corresponds to that
extent to the control of a transistor. Controls of this type are
described as regards their mode of operation in Kirshner, 1966, Fluid
Amplifiers, McGraw-Hill, pp. 193 to 203.

[0017] It is possible to provide here both two-sided control where the
controlling mass flow is supplied via two control supply lines to the
fluidic switching element in the area of the branching point, and
one-sided control where the controlling mass flow is supplied via one
control supply line to the fluidic switching element in the area of the
branching point. With two-sided control, the fluidic control element is
as a rule designed such that the cooling gas flow splits into the two
outlet branches without the controlling mass flow. The controlling mass
flow subjected to a certain control frequency leads to the cooling gas
flow being alternatingly routed into one of the two outlet branches. With
one-sided control, the fluidic control element is designed such that the
cooling gas flow is routed without the controlling mass flow into one of
the two outlet branches and to that extent creates a monostable
situation. The controlling mass flow subjected to a certain control
frequency leads to the cooling gas flow being diverted for a certain
period--depending on the control frequency--to the other of the two
outlet branches.

[0018] It is pointed out that control of the fluidic switching element by
means of a controlling mass flow only represents one exemplary
embodiment. Alternatively, the fluidic switching element can also be
designed such that it manages without any external control. To do so, the
fluidic switching element is for example designed such that it vibrates
at a characteristic frequency due to its geometry, possibly in
conjunction with internal feedback ducts between outlet ducts and control
ducts.

[0019] It is provided that the ratio between the frequency f of the
pulsating impingement jet, the mean outflow velocity u of the cooling gas
from the outlet openings and the diameter d of the outlet openings is
such that the Strouhal number Sr formed with these values according to
the formula Sr=f*d/u is in the range between 0.2 and 2.0, in particular
in the range between 0.6 and 1.4 and preferably in the range between 0.8
and 1.2.

[0020] It can be provided that the fluidic switching element is designed
in a partition wall arranged at a distance from an impingement wall to be
cooled, where the annular swirls formed by the impingement jet impact the
impingement wall and cool it with high efficiency. The impingement wall
is here arranged on the one side of the partition wall. The fluidic
switching element is supplied from the other side of the partition wall
with cooling gas, for example via a volume filled with cooling gas.

[0021] The fluidic switching element can have in its specific embodiment a
plurality of variations. It can for example be provided that the outlet
branches of the fluidic switching element are designed curved or
straight. The area of the branching point at which the inlet branch
splits into at least two outlet branches can also have various
embodiments. In one design variant, it is provided to this end that the
branching point of the fluidic switching element forms two feedback lobes
inside which part of the cooling gas is routed back in the direction of
the inlet branch instead of flowing into one of the outlet branches. This
facilitates and accelerates switching of the switching element into the
other state, allowing higher switching frequencies to be achieved.

[0022] In a further embodiment of the invention, it is provided that the
apparatus has a plurality of fluidic switching elements arranged in the
form of a one- or two-dimensional array. It can be provided here in one
design variant that two fluidic switching elements are arranged adjacent
to one another and that two outlet branches of these adjacently arranged
fluidic switching elements are aligned with one another such that annular
swirls with double frequency are present at a defined distance from the
fluidic switching elements. The impingement wall is arranged at the
defined distance, so that annular swirls from two outlet branches of two
switching elements impact an affected wall area such that the latter is
subjected to annular swirls with double frequency, with the advantage of
a further improved cooling.

[0023] In accordance with a second aspect, the invention relates to a
turbomachine with an apparatus in accordance with Claim 1. The fluidic
switching element is here arranged in the turbomachine such that the
annular swirls formed by the impingement jet exiting the outlet openings
of the fluidic switching element impact a wall or surface of the
turbomachine to be cooled.

[0024] The turbomachine component is for example a turbine. The wall or
surface to be cooled is that of a casing, a casing liner or a turbine
blade of the turbine. In one design variant, the surface to be cooled is
for example the rear face of an insert ring (also referred to as "liner")
arranged in the area of the turbine rotor on the circumference of the
turbine casing. The apparatus in accordance with the invention can
however also be used for cooling any other structures of a turbomachine
having an impingement wall.

[0025] In a third aspect, the invention relates to a method for the
creation of an impingement jet generating annular swirls. It is provided
that cooling gas is supplied in one fluidic switching element
alternatingly to at least two outlet branches of the fluidic switching
element, where in each outlet branch an impingement jet pulsating at a
frequency f is generated and forms annular swirls after leaving the
fluidic switching element.

[0026] The present invention is more fully described in light of the
figures of the accompanying drawing showing several exemplary
embodiments. In the drawing,

[0027]FIG. 1 shows in schematic representation a fluidic switching
element for the creation of an impingement jet generating annular swirls,

[0028]FIG. 2 shows in schematic representation an exemplary embodiment of
an impingement cooling configuration using a plurality of fluidic
switching elements,

[0029] FIG. 3 shows in schematic representation a further exemplary
embodiment of an impingement cooling configuration using a plurality of
fluidic switching elements, with a doubling of the impact frequency of
annular swirls between adjacent switching elements being achievable,

[0030] FIG. 4 shows in schematic representation a further exemplary
embodiment of an impingement cooling configuration using a plurality of
fluidic switching elements, with the switching elements being designed
for achieving high switching frequencies, and

[0031]FIG. 5 shows a partial view of a turbine of a jet engine, with a
casing of the turbine being cooled by means an impingement cooling
configuration in accordance with FIGS. 2 to 4.

[0032]FIG. 1 shows a fluidic switching element 1 used to create an
impingement jet generating annular swirls. The switching element 1 has an
inlet branch 2 that splits at a downstream branching point 4 into two
outlet branches 31, 32. The inlet branch 2 is supplied at an inlet
opening 21 with a cooling gas G which is for example air. To supply the
inlet branch 2 with a cooling gas, it is for example provided that above
the fluidic switching element 1 a volume is located in which the cooling
gas is contained with a defined pressure. Due to this pressure, the
cooling gas G flows into the inlet branch 2 of the fluidic switching
element 1 at the inlet opening 21. Alternatively, the cooling gas can for
example be supplied using a hose connected to the inlet opening.

[0033] It is provided that the cooling gas is routed alternatingly into
only one of the two outlet branches 31, 32. To achieve this, a control is
provided which includes two control supply lines 51, 52 which issue at
the level of the branching point 4 into the inlet branch 2 and which are
for example designed symmetrical to one another. A controlling mass flow
S is provided via the control supply lines 51, 52 which supplies a
controlling gas, which can likewise be air, to the area of the branching
point 4. The controlling mass flow S is subjected to a defined frequency
and amplitude. The controlling mass flow S is here considerably smaller
than the main mass flow, which is formed by the flow of the cooling air G
through the fluidic switching element.

[0034] The periodic fluctuation of the controlling mass flow S can be
generated for example by exploiting turbine- or compressor-generated
fluctuations, or by separate resonators or generators.

[0035] Supplying the control supply lines 51, 52 with a controlling mass
flow S of defined frequency achieves control over which of the outlet
branches 31, 32 the cooling gas G (the main mass flow) flowing in the
inlet branch 2 is routed into. For example, depending on the phase angle
at the control supply lines 51, 52, the cooling gas is routed into one or
the other of the outlet branches 31, 32. The cooling gas is switched back
and forth between the two outlet branches 31, 32. Numerous design
variants for a control of this type are possible here.

[0036] Supplying a periodic and relatively small controlling mass flow
generates a periodic high-amplitude on/off behaviour of the main mass
flow in both outlet branches 31, 32. A pulsed impingement jet P with
periodic on/off behaviour at a frequency f of high amplitude is thus
formed in both outlet branches 31, 32. Accordingly, an on/off jet is
provided at the outlet openings 8 of the two outlet branches 31, 32. This
is achieved without the main cooling mass flow G having to be
periodically interrupted, and in particular without active interrupter
actuators having to be used or a fluctuating high-amplitude supply of the
main cooling mass flow G being necessary.

[0037] The amplitude of the on/off jet provided at the outlet openings 8
is disengaged from the amplitude of the controlling mass flow applying at
the control supply lines 51, 52.

[0038] An impingement jet P is emitted at each of the two outlet openings
8 of the two outlet branches 31, 32. Each impingement jet P has during
its "on" phases a mean outflow velocity u with which it exits the outlet
opening 8. If d is the diameter of the outlet opening 8 of the respective
outlet branch 31, 32, and f the frequency of the on/off jet, then the
Strouhal number Sr is determined from these parameters as follows:

Sr=f*d/u.

[0039] The parameters of frequency f, diameter d of the outlet opening 8
and mean outflow velocity u are here set such that the Strouhal number Sr
is between 0.26 and 2.0. The Strouhal number is preferably in the range
between 0.8 and 1.2. With these values for the Strouhal number, the
on/off-pulsed impingement jet P automatically generates annular swirls 7,
shown schematically in FIG. 1, after leaving the outlet opening 8.

[0040]FIG. 2 shows a first exemplary embodiment in which fluidic
switching elements 1, as described with reference to FIG. 1, are used to
obtain an impingement cooling configuration in a turbomachine. The
impingement cooling configuration is for example provided inside a cavity
of a turbine component. The switching elements 1 generate, as described
with reference to FIG. 1, a pulsed impingement jet P with periodic on/off
behaviour of a frequency f and high amplitude in the respective outlet
branches 31, 32, with the impingement jet P generating annular swirls 7.

[0041] The impingement cooling configuration of FIG. 2 includes a
partition wall 11 having two parallel surfaces 111, 112. A plurality of
fluidic switching elements 1 in accordance with FIG. 1 is provided in the
partition wall 11 in a linear arrangement. The fluidic switching elements
1 can here be arranged in the form of a one-dimensional or
two-dimensional array.

[0042] The arrangement of the fluidic switching elements 1 in the
partition wall 11 is such that the respective inlet opening 21 of the
inlet branch 2 is in the plane of the one surface 111, and the respective
outlet opening 8 of the outlet branches 31, 32 is in the plane of the
other surface 112. The cooling gas G is supplied from the side of the
surface 111. The controlling mass flow S is provided by a unit 53 which
is for example a compressor, a turbine, a resonator (e.g. Helmholtz
resonator) or a low-amplitude actuator.

[0043] The impingement cooling configuration furthermore has, at a
distance from the partition wall 11, an impingement wall 12 to be cooled.
The impingement wall 12 has a surface 121 impacted by the annular swirls
7 generated by the switching elements 1. The annular swirls 7 provide a
high cooling effectivity, since the periodic occurrence of the annular
swirls 7 leads to a periodic renewal of the fluid and temperature
boundary layer on the surface 121.

[0044] The partition wall 11 and the wall 12 to be cooled are generally
arranged curved relative to one another, i.e. their corresponding
surfaces 112, 121 are each curved. This is not illustrated in the
schematic representation of FIG. 2. However, other embodiments are also
possible, for example an angled or parallel arrangement of the partition
wall 11 and the wall 12 to be cooled.

[0045] A cooling air duct 13, via which the cooling air is removed after
impacting the surface 121 to be cooled, is located between the partition
wall 11 and the wall 12 to be cooled.

[0046]FIG. 2 shows further fluidic control elements 1', which differ from
the fluidic switching elements 1 in that one-sided control is provided.
To do so, the fluidic switching element 1' has not two, but only one
control supply line 51. The functional principle is such that without the
controlling mass flow, the cooling gas G would always be routed into one
of the outlet branches 31, 32 (monostable state). It is achieved by the
controlling mass flow that the cooling gas is periodically diverted to
the other of the outlet branches.

[0047] In design variants, the impingement cooling configuration has only
switching elements 1 with two-sided control, only switching elements 1'
with one-sided control, or both switching elements 1, 1' with one-sided
and with two-sided control.

[0048] FIG. 3 shows a modification of the impingement cooling
configuration of FIG. 2 where the outlet branches 31, 32 of the fluidic
switching element 1 that adjoin the branching point 4 leave the partition
wall 11 at an angle not equal to 90°. The two outlet branches 31,
32 are for example each designed in a straight line here. This leads to
areas 121a of the surface 121 to be cooled being subjected to both the
pulsed impingement jet P of the one outlet branch 32 of a fluidic element
1 and the pulsed impingement jet P of an outlet branch 31 of an adjacent
fluidic switching element 1. This leads to a doubling of the impact
frequency of the annular swirls, since the areas 121a are subjected to
annular swirls of adjacent fluidic switching elements 1 with phased
impacts.

[0049] FIG. 4 shows a modification of the described impingement cooling
configuration in which the fluidic switching elements 1 are designed for
achieving high frequencies f in the range of more than 10 kHz in the
pulsation of the impingement jet P. To do so, the switching element 1 has
in the area of the branching point 4 two lateral lobes 41, 42
symmetrically below the inlet of the control supply lines 51, 52. Inside
the lobes 41, 42, some of the cooling gas G supplied via the inlet branch
2 is routed back in circular manner, thereby allowing switchover to be
achieved more easily and quickly. Fluidic switching elements of this type
are known from U.S. Pat. No. 3,434,487 A. Lateral feedback lobes of this
type can be provided regardless of the form of the outlet branches 31, 32
and regardless of whether the control is two-sided or one-sided.

[0050]FIG. 5 shows an example of application where an impingement cooling
configuration of the type described is used for the cooling of a casing
and/or lining of the turbine 100 of a jet engine. In accordance with the
sectional representation of FIG. 1, the turbine 100 has stators 110 and
rotors 120. A circumferential casing 130 is provided that delimits a flow
duct 140 through the turbine 100 radially outwards. A lining element in
the form of an insert ring 150 (also referred to as "liner") is arranged
towards the flow duct 140 on the circumferential casing 130 and adjoining
the rotor 120. An insert ring 150 of this type is used to minimize the
annular gap between the tip of the rotor 120 and the casing 130.
Alternatively, the casing 130 can however also be designed without an
insert ring 150 of this type.

[0051] On that side of the casing 130 facing away from the flow duct 140,
an impingement cooling configuration 160 is provided that has several
fluidic switching elements 1. The impingement wall is formed in this
exemplary embodiment by the casing 130 or its surface facing away from
the flow duct 140. The controlling mass flow is for example made
available by using turbine- or compressor-generated fluctuations.

[0052] The impingement cooling configuration is for example designed such
that the diameter d of the outlet openings of the fluidic switching
elements 1 is 1.4 mm. The mean outflow velocity is 17 m/s. The frequency
f of the pulsation of the impingement jet is 10 kHz. The control
frequency for switching of the fluidic switching element is, depending on
the model, between 10 and 100 kHz. These values result in a Strouhal
number of 0.82. Hence the impingement jet periodically generates annular
swirls achieving a high cooling effectivity when cooling the casing 130
and the insert ring 150.

[0053] The present invention is restricted in its design not to the
exemplary embodiments presented above, which must be understood merely as
examples. In particular, the fluidic switching elements can be designed
in a different way, for example having more than two outlet branches
and/or being switched in a different way. Furthermore, the arrangement of
the fluidic switching elements in a one- or two-dimensional array, for
example, must be understood merely as an example. The impingement wall
can be part of any inner or outer wall of a component of a turbomachine.